DE1690224B1 - BATHROOM FOR ELECTRONIC COPPER PLATING OF PLASTIC PANELS - Google Patents

Description

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The invention is concerned with the production of metallic medium to convert copper (I) oxide,

so-called hole-plated printed circuits. probably has a catalytic effect on the reaction

In this manufacturing process, the reaction equation is used:
commercially available non-laminated carrier materials, e.g. B.

in the form of carrier plates or carrier films or 5 Cu +++ 2H CHO + 4 OH ^ 2HCOO + 2H ₂ O

like that. With these not with a copper foil ' ² ~ * ~ ^u '

laminated carriers will lead to the pattern whereby it will grow wild as a result of the self-decomposition of the bath

built up in layers and the figuration of the deposit comes.

tion pattern generated by etching. It is therefore the object of the invention to provide a bath for the accordingly ^ to a manufacturing process after the io electroless copper plating of plastic plates under

Additive etching method. Indicate the use of a copper plating bath,

There is already a method for the production of by which on the printed circuit boards immersed therein on a carrier plate made of plates, a copper layer is deposited electrolessly Isolation material known (German Auslegeschrift is, whereby the self-decomposition of the copper plating 1206 976), in which the carrier 15 should be prevented from bathing after activation.

is pre-coppered without current, the pre-coppered according to the invention this is achieved in that

Carrier is covered with an anti-etch varnish - and to stabilize the bath metal complex salts as

in such a way that the cables remain free - the stabilizers are attached.

The stabilizers capture the traces of copper pre-copper plating and the pre-copper plated holes and thus prevent the formation of Cu ₂ O. In the opposite walls then galvanically except for the requirement for stabilizers with free cyanide ions Thickness are increased, after which the etching is thereby also the advantage that the protective varnish is removed during operation and then the required higher concentration of this copper plating and the main copper plating at the same time plex salts, the baths are better controlled and thus etched over time by means of differential etching. 25 can be watched.

The complexes so far used in the known processes are such. B. the potassium electroless Metal baths have significant disadvantages of hexacyanoferrate (yellow blood liquor salt) or potassium. The well-known silver baths for currentless tetracyanoic colate.

Silver plating are too expensive and too unstable and result in such copper metal baths according to the invention for

In the manufacture of printed circuit boards, electroless copper plating can therefore be as follows

turns, putting together a »silver hike« on the top of the girder:

area which the circuits are electrically unusable y
power.; - ■■■■■■■ "-

Instead of silver, nickel can also be electroless ^ ! Γν ^ Τ ??

get knocked down. However, nickel is due to 35 Tr ^ f · \ i rm

its poor conductivity for printed circuit- ^ ^g H; ^eie Λ Jr λ

unsuitable. Even if nickel is currentless as ¹ ^ S ^ ^ο ™ ^ Γι ^ .... «. _Λ

thin pad and as an electrode for the galvanic °> ⁰⁵ § ^K * t ^Nl ( ^CN ^ (stabilizer)
Application of a thicker copper layer used
would, it would because of the poor conductivity- 40

Ability to different thicknesses of the copper layer 10 g CuCl ₂ · 2 H ₂ O

to lead. Further difficulties would arise, 56.5 g of K NaC ₄ H ₆ O ₆

if the nickel in addition to the copper in the so-called 14.7 g of free NaOH

Differential etching must be etched out. 12 g formaldehyde

In the known method, after a 45 °> ⁵ S ^K * \ P ^e (GN) ₆ ] (stabilizer)
greasing, which is preferably carried out in an alkaline degreasing bath, the surface of the carrier plate HI
with commercially available or already known AM 10 g CuCl ₂ · 2 H ₂ O
solutions activated. Treatment with 56, SgKNaC ₄ H ₄ O ₆
such activation solutions are pretreated with 50 10 g of free NaOH
known per se for electroless metallization. 8.7 g formaldehyde
They create discrete spots on the not me- 1.3 g K ₄ [Fe (CN) ₆ ] \ _{Q. Ky} .
activated metallic carrier bodies, on which the 0.6 g of K ₃ [Cu (CN) ₄ ] J ^{öiaDlusaioren}
subsequent electroless * metallization metal ions -

should be firmly attached. The surface of the carrier body 55 The electroless metallization "pre-plating", the

is covered with metal nuclei, which are usually needed in a thickness of about 4 μ

serve further additive structure of the conductive layer. is carried out with bath I and II advantageously at

The previously known solutions for the currentless room temperature, while for the deposition of thicker

Metallization with copper, however, have now operated the post-copper layers in bath III at around 45 ° C

part of the fact that it collapses easily and thus becomes 60,

prevent the generation of thicker layers. However, the invention is not limited to the precise

The maintenance of these temperatures and concentrations during electroless metallization Reduction of the copper (II) ion to metallic copper is limited, but this can be done depending on the situation via the oxidation level copper I. Be adapted at the turn.

Electroless copper baths used up to now are 65 After this electroless metallization (presumably a low proportion of copper (TI) ion only on plating) with a thickness of usually 4 μ , the copper (I) level is reduced. That is so in the, the negative conductor pattern is then after well-known baths enriching copper I, which is in the alkaline process either in the screen printing or after the

Photoresist or offset process applied to the pre-plating. The uncovered areas that So correspond to the positive line pattern, are now galvanized by means of acidic copper baths up to the desired thickness of e.g. B. 35 μ built.

The carrier plates pretreated in this way are sintered ^{at temperatures between 100 and 180 ° C. after the customary soaking.} The most favorable temperature to avoid damage to the carrier plate material is usually 160 ° C for 2 hours.

When electroplating the main plating, which is built up on the approx. 4 μ thick pre-plating, these 4 μ, _# <ϋε on the negative conductor pattern are removed again by etching, taking into account that the main plating has a thickness of 35 + 4 = 39 μ receives. After 4 μ has been etched off, the pre-plating disappears and the main plating is given its exact thickness of 35 μ.

The technical characteristics of the printed circuit boards produced by this process are exceptionally good and in some cases exceed the previously known quality.

The insulation resistance measured according to the standardized ring electrode method is 3 · 10 ⁵ Ω in the carrier plates made of phenolic hard paper according to the invention. The adhesive strength (peel strength) between the copper cladding and the carrier (measured in accordance with DIN 40802 No. 5.5.2.1. And No. 5.5.2.2. Of December 1960) reaches the extraordinarily high value of over 2500 p / inch (around 1000 p / cm).

In order to be able to solder the finished boards well, they are in a with hydrogen peroxide or ammonium persulphate provided sulfuric acid bath.

In order to protect the plates against corrosion during storage, they can be further treated as follows will:

Coating with a solderable protective varnish, currentless Coating of corrosion-preventing metal and / or immersion in water displacers.

Claims (8)

Patent claims: 1. Bath for the electroless copper plating of plastic plates using a 40 copper bath, through which a copper layer is deposited electrolessly on the plastic plates immersed therein, characterized in that metal complex salts are added as stabilizers to stabilize the bath. 2. Bath according to claim 1, characterized in that K ₂ [Ni (CN) ₄ ] is added as a stabilizer. 3. Bath according to claim 1, characterized in that K ₄ [Fe (CN) ₆ ] is added as a stabilizer. 4. Bath according to claim 1, characterized in that K ₃ [Cu (CN) ₄ ] is added as a stabilizer. 5. Bath according to claim 1, characterized in that the stabilizers according to claims 3 and 4 are attached together. 6. Bath according to claim 2, characterized by a stabilized copper plating bath with substantially the following composition: 15 g CuCl ₂ · 2 H ₂ O 40 g K Na C ₄ H ₄ O ₆ 13 g free NaOH 11 g formaldehyde 0.05 g K ₂ [Ni (CN) ₄ ] 7. Bath according to claim 3, characterized by a stabilized copper plating bath with substantially the following composition: 10 g CuCl ₂ · 2 H ₂ O 56.5 g K Na C ₄ H ₆ O ₆ 14.7 g free NaOH 12 g formaldehyde 0.5 g K ₄ [Fe (CN) ₆ ] 8. Bath according to claim 5, characterized by a stabilized copper plating bath with substantially the following composition: 10 g CuCl ₂ · 2 H ₂ O 56.5 g K Na C ₄ H ₄ O ₆ 10 g free NaOH 8.7 g formaldehyde 1.3 g K ₄ [Fe (CN) ₆ ] 0.6 g K ₃ [Cu (CN) ₄ ]